A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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2
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19 views

MANOVA as protection against Type I errors

OK, so I have absolutely scoured the internet, and it appears that there is consensus (among people who really care about Type I error) that doing a MANOVA before doing multiple ANOVAs does nothing to ...
4
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1answer
35 views

Why exactly is normality an assumption in a T-test but not a Wilcox rank sum/Mann Whitney U test when obtaining a p-value?

In addition to the question, please do correct anything below that I have incorrect. I understand how the test statistics for a t-test and WRS/MWU test are calculated. In a t-test, $t=\frac{\bar ...
0
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0answers
10 views

Is there an accepted way to compare within all demographic categories (e.g., within males, within females, within whites, etc.) using MANOVA

I have three experimental groups (group A, group B, and group C), and gave all participants the same 50-question questionnaire. I then can run a MANOVA to determine if their responses (quantitative) ...
0
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0answers
34 views

Which statistical test to use on mean data?

I have sets of data from two sample A and B. the data in sample A and B are the average mean of the population sample. Examle, sample A has list of data. each data in he sample is a an average value ...
1
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1answer
14 views

F-test of joint significance vs multiple t-test for regression parameters? [duplicate]

In the context of linear regression, I don't understand why you need to perform an F-test for the H0 that all parameters are zero, instead of just looking at all the t-tests for each parameter. I ...
0
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0answers
32 views

Which statistical test should I use for my report which has Two sets of data?

I have collected data from load testing a website. The basic Idea here is that, a website hosting on a server is tested by increasing number of virtual users. Example, there are 5 iterations in each ...
2
votes
1answer
31 views

Compare two t-statistics

In a nutshell: I have performed two t-tests (A und B, each two-samples/paired). Both found significant differences. Can I tell, whether the difference observed in comparison A is significantly larger ...
0
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0answers
27 views

Contradiction between Pearson's correlation coefficient and t-test results

I've been analysing data between cliff height and average erosion rate. The data is parametric so I used Pearson's correlation and found that I got a coefficient of 0.017. When I applied a 2-tailed ...
0
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0answers
25 views

Basic Power test and Power test using ncp do not match

I am referencing 18.5 section of http://www.cyclismo.org/tutorial/R/cholesterol.html ,data is available to download and test. The case study asks to perform a ...
1
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0answers
18 views

Can I use a partial eta squared on t-test results?

I am currently trying to decide which effect size is the most appropriate for my results. I have conducted a repeated measures ANOVA, there are five variables in the ANOVA, all of which are within ...
0
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0answers
27 views

T-test formula when population standard deviation is known [duplicate]

I got this question from my mentor. Marks obtained by 10 MBA students in Statistics paper (out of 50) is given below. 20.5, 18.25, 10.23, 15.47, 35.62, 47.64, 12.30, 29.65, 38.5, 14.79. Test whether ...
0
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0answers
18 views

How do I calculate the effect-size of an unequal sample size independent t test?

Given the following parameters, how do I calculate the effect size of an independent unequal sample size t test? ...
2
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2answers
47 views

Student's t-test with a covariate?

I am testing the different between some variables $X$ and $Y$ using the Student's t-test. I suspect that there might be a latent variable $Z$ that has an effect on both $X$ and $Y$. How could I ...
0
votes
1answer
22 views

Is it common practice to correct for multiple comparisons with multiple ANOVAs?

I gave three groups of participants (say groups A, B, and C) different treatments, then gave all groups the same questionnaire. The questionnaire has ~50 questions. I then run ANOVA on each of the ...
0
votes
0answers
23 views

how to do a t-test in matlab of 2 data(matrix of 3 ex: 180*820*23) [closed]

how to do a t-test in matlab of 2 data(X and Y) and X and Y have each 9 signals those signals are matrix of 3 ex: 180*820*23 or 180*820*30 etc..) and which i have to take the peak from each signal, so ...
-1
votes
1answer
51 views

Applying the T-test [closed]

So far I have calculated the sample means $\overline{A} = 0.75$ and $\overline{B} = 2.33$. Using these I computed the sample variances: $S_A^2 \approx \frac{28.805}{9} = 3.2005$ and $S_B^2 = ...
0
votes
2answers
42 views

Difference between F-test and separate t tests on each variable?

Why can't we separately test each variable(using t-test), whether or not it is equal to 0? Why should we use the F-test for checking if all coefficients combined are equal to 0?
0
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0answers
23 views

Probit with one variable or t-test

I have a dataset with observations from two consecutive elections with data on party choice and the voters income. I want to test if an increase in income, compared to a decrease, causes voters to ...
0
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0answers
14 views

LME, t-test and glht

I am doing some light simulations, but came across the following problem. I cannot obtain the same p-value as a paired t-test as it does for multiple comparison and LME. ...
2
votes
1answer
49 views

Normality, and when to use t-test vs. Mann-Whitney U-test?

I am looking for a few rules of thumb of when to determine that my data is 'normal enough' to use a t-test vs. a Mann-Whitney U-test. From what I have read, most real world data sets are non-normal, ...
0
votes
1answer
49 views

Cohen's D: Should I use raw data, log transformed data or back transformed data?

I am a doctor and right now I am doing medical research. I have some questions about cohen's d. I try to research it on the internet but it seems there is not much answer to this question. My project ...
0
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0answers
23 views

t-test with unequal sample size, very large group and very small group [duplicate]

If I have data for 2 group with unequal sample size, first group $n_1=81$, second group $n_2=72000$. Can I still do a t-test for comparing the mean difference between these 2 groups?
0
votes
1answer
21 views

Comparing mean differences between groups when standard deviation in one of them is 0

I was wondering if it is possible and -if yes- what are the implications when one is trying to compare mean group differences of a continuous variable that varies in one group but is a constant number ...
1
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0answers
29 views

Weak correlation but significant t test [duplicate]

I have two variables. Sense of belonging and anxiety. I found a Pearson's correlation that was weak but significant. The significance was probably due to sample size (n=400). Then I conducted a t-test ...
0
votes
1answer
11 views

Additional T-Tests after Mixed-ANOVA required/ useful to test initial equalness of groups?

I am currently evaluating a mixed research design, where a treatment and a control group are evaluated over time. I am interested in the effectiveness of the treatment and therefore evaluate the ...
0
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0answers
11 views

obtaining test statistics within two population with (possibly) multiple samples from the same subject

Given two groups of people in which each subject can rate multiple items I would like to check if any group in general rates the items with significantly higher (or lower) scores. To give a specific ...
0
votes
1answer
25 views

Analysing data from summary table on R (interactions)

If I want to test whether data[,1]:setB is equal to 0 or not, do I just use the given t value and p value or do I need to add it with the data[,1] values? looking at the p value of data[,1]:setB, I ...
0
votes
1answer
9 views

If one of my samples has zero variance, can I perform an ANOVA or are pairwise one-sample t-test's more appropriate?

I know only the basics about statistics, and I work in a biological lab where most people know less than I do. I was hoping someone who is a bit more informed about statistics to help me out. I have ...
0
votes
0answers
61 views

Is this good statistics?

I have the mean of 2 samples, as well as the standard deviation. I wanted to see if I could run a t-test on this data, and using the standard deviation and my knowledge of the 68–95–99.7 - I did the ...
0
votes
1answer
24 views

Poisson distribution with glmer - pairwise comparisons

I am analyzing counting data from a field experiment using the glmer procedure according to a Poisson distribution. The model works and I can visualize the results ...
0
votes
0answers
7 views

Is there an option to test the difference in correlations from two independent samples in SPSS?

My question is essentially equivalent to the title: Is there an option to test the difference in correlations from two independent samples in SPSS? I found this online calculator and know the ...
0
votes
1answer
41 views

Results of 2-sample t-test does not seem intuitive; wrong procedure?

I have data shown below, with a response variable tabulated by hour (x-axis) as well as numerous other factors: larger chart available here I want to see if the colored points (red, light and dark ...
2
votes
2answers
25 views

Correct data preparation for paired T-test

I've processed my data in two ways to determine significant difference, one method suggests a very high significant differences (p = 0.0000...), while the other returns non-significant results (p = ...
0
votes
0answers
20 views

ANOVA not significant but t-test significant

I have survey responses from people from 10 countries (sample range from 10 to 71 response per country) and I am trying to see if there are significant differences between the people of each country ...
1
vote
1answer
30 views

Comparing Means: Multiple Dependent Variables

I am using school-level data to compare mean scores for two groups (Group A schools and Group B schools), as measured by a series of indicators: 1) grade-level exam percentile, 2) percent of male ...
1
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0answers
17 views

How should I calculate required n for minimum power of a sequence of parallel or simultaneous tests?

I am concerned with the practical situation in which I design a 'no-budget' split-ballot 2 x 1 experiment. We have money for $n=80$ cases in total, thus $n=40$ in each of two groups. In total I will ...
0
votes
0answers
61 views

t-statistic vs two-sample t-tests

When and in which context is the t-statistic used? $ t = \frac{\hat{\beta} - \beta_0}{se(\hat{\beta})} $ where $\beta_0$ is a non-random, known constant, which defines the null-hypothesis in the ...
1
vote
0answers
28 views

F-Test for Equality of Variances with Weighted Survey Data

I would like to use an F-Test for Equality of Variances on a variable to compare two groups. Normally, this would be done with an sdtest command in Stata or a ...
1
vote
2answers
41 views

ttest or wilcoxon

for a user study I want to compare some tasks. Each tasks has 2 conditions on a intervall scale. From each task I want to test the the conditions with: a t-test if both samples are on a normal ...
2
votes
1answer
34 views

How do I statistically test whether two intervention types have significantly different effects in a meta-analysis?

I have the following problem: I am researching the difference in effects (as measured by standarized mean differences (SMD)) of two intervention types. (let's call them intervention 1 and intervention ...
4
votes
1answer
380 views

95% confidence intervals and the null hypothesis

I have performed an unpaired t-test comparing the means of two groups. My hypothesis was that the stroke group mean would be significantly higher than the control group mean. However, the t-test ...
2
votes
2answers
241 views

Statistically significant?

I am new to statistics and so any help would be greatly appreciated! I have done a study looking at the number of samples being sent to the lab for patients with UTIs in a GP practice. I then ...
0
votes
0answers
20 views

Test statistics in IR (t-test vs Wilcoxon vs signed test)

I have just read this paper about different test statistics one could use in Information Retrieval (IR), discussing whether Wilcoxon, Sign-test or Student t-test would be more reliable for comparing ...
2
votes
1answer
24 views

Missing data paired samples t-test

I have a list of insurance policies that filed claims in pre/post periods. I am trying to test whether the average cost of insurance claims per policy varied. Some of my policies don't have any claims ...
1
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0answers
17 views

How can I tease apart the role two variables play in an outcome?

I was wondering what type of statistical test I can use to find the role each variable plays in this scenario. We have an experiment set up with four groups (we are using drosophila flies). Group ...
0
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0answers
42 views

Unpaired t-test: large samples, unequal variances, unequal sample sizes

I a have two independent samples one with more than 700 observations and the second with more than 500 observations. I firstly use Cramér-von Mises test to test normality just to check how non-normal ...
0
votes
1answer
39 views

T-test or regression?

I have the following kind of data id age x 1 22 2.1 2 25 2.3 3 50 1.3 where $x$ is some measurement variable. I would like to show ...
3
votes
3answers
342 views

How to interpret negative 95% confidence interval?

I have performed an unpaired t-test on two groups of data: Group 1 (control): mean = 0.087 (n = 15) SD = 0.028 Group 2 (treatment): mean = 0.115 (n=12) SD = 0.042 The t-test ...
0
votes
0answers
19 views

In a two-way ANOVA, F-statistic for one factor is less than one and not significant. Much higher in t-test?

I conducted a two-way ANOVA (factors=season of birth and ethnicity) and found that the effect of ethnicity (Pakistani and White British) did not have a significant effect on child weight F(1, ...
0
votes
1answer
28 views

Mixed way ANOVA

I have two variables (group, achievement level). I want to check the effect of an intervention on different achievement levels. For example, I want to check whether there is an increase in achievement ...